1. Field of the Invention
This invention relates to a direct connection telephone system, and in particular, to an office line holding circuit with an automatic release function.
2. Description of the Prior Art
The direct connection telephone system has a plurality of telephone sets which are directly connected to a pair of subscriber's drop terminals of a common office line of paired two wires.
In actual use of the direct connection telephone system, a plurality of telephone sets of the system are generally disposed at different places remote from one another, for example, one being on the first floor with the other on the second floor in a house. During a call from the telephone set on the first floor, it often happens that the call is desired to be continued by another telephone on the second floor. This is realized by leaving the first floor telephone set in the off-hook condition and taking the handset of the second floor telephone set off the hook. However, it is required to reset the first floor telephone set in the on-hook condition after taking off the handset of the second floor telephone set, or after the end of the telephone call on the second floor. Otherwise, any telephone call by the other subscribers cannot be, thereafter, received.
This is a disadvantage of the direct connection telephone system.